As far as they are presently known, the electronic modules intended to equip transaction cards appear generally in the form of a wafer designed to be incorporated into a corresponding opening of the card body located in a corner of the latter and including a memory and an integrated microprocessor in the form of a single chip or two chips connected together by electrical conductors, a set of contact pads, often to the number of eight, coupled solely to the microprocessor and an insulating body in which are concealed all the other elements with naturally the exception of the conductive pads or electrodes which must be made accessible for the connection members of an apparatus, for instance a computer terminal in which the card is intended to be introduced. In certain cases the insulating body which defines the form of the wafer and which assures protection of the elements which it surrounds comprises a support portion and a covering portion, in others it comprises a homogeneous encapsulation.
On the other hand independently from the questions connected with the integrated circuit itself, as for instance those of knowing which information the memory must stock, which functions the microprocessor must perform and in which manner such memory and microprocessor must be conceived, the preparation of the electronic modules gives rise to a certain number of problems in view of the numerous demands to which they must respond.
Initially, a microcircuit card for payments must have the same format as the well-known card having standardized magnetic tracks, the length of which is 85 mm, the width 54 mm and the thickness 0.76 mm (ISO standards) or at least dimensions close thereto in order to avoid bulkiness and to be readily manipulated.
If one takes into account that initially a thickness of 760 microns corresponds roughly only to only twice that of an integrated circuit chip without protection, that secondly the portion of the card surface which can be allocated to the electronic unit is very limited, being given that the major portion of such surface must be reserved to inscriptions such as the designation of the party issuing the card, identity of the bearer, a signature, information concerning utilization and eventually a photo and that, thirdly, the conductive pads must be sufficiently large in order that the contact with the connection members of the apparatus be assured and good, it will be readily and rapidly seen that one may not use standardized circuits already encapsulated or encased such as those which are presently found on the market and which are much too voluminous.
One is thus oneself obliged, in order to manufacture the electronic modules from bare integrated circuit chips, to provide the network of interconnections which enables electrically connecting these chips with the exterior and among themselves if there should be several in the same module and to assure the protection of the assembly which is naturally very fragile, above all at the junctions between the conductive portions (connection terminals of the chip, wires, etc.).
It is necessary furthermore to avoid that external agents such as light or humidity cause deterioration of the circuit or disturb the operation thereof.
It will likewise be noted that the cards must be such as to be adapted to mass production and at a very low manufacturing cost, above all for cards in which a certain value is initially entered which one pays when buying them and which when this value has been exhausted must simply be thrown away.
The conductive pads or electrodes likewise form the object of standards as to their positions on the card, the maximum dimensions which their surfaces may present and finally the functions which may be attributed to them. On this subject one may readily consult the project of ISO standard No. 7816/2.2 established by the technical committee TC 97. In this document there are assigned to the eight electrodes designated from C1 to C8 precisely defined functions, for instance to electrode C1 the energization voltage VCC, to electrode C3 the clock signal CLK, to electrode C5 the ground GND and to electrode C7 the input and output data I/O. It will be readily understood that this order is not necessarily going to correspond to that which has been chosen for the chip to be employed, in such a manner that perhaps it may be necessary to envisage detours of the conductors coupling said electrodes to the connection terminals of the chip. At least one embodiment of the electronic module according to the present invention should enable these detours in order to adapt a chip having connection terminals arranged according to any order whatsoever to the electrodes of a standardized electronic module.
As in the present invention, the module described in document DE-A No. 3 248 385 comprises two units. The first unit includes a first substrate onto which are imprinted the electrodes on the visible face, the opposite face of the substrate bearing metallizations coupled to the electrodes by means of metallized holes. The second unit comprises a second substrate and metallized conductors intended to couple the terminals of a chip to the metallization borne by the first substrate. Under each of these conductors there is pierced an opening thanks to which it is possible to solder the conductor to the corresponding metallization of the first substrate. It is noted however that these conductors cover entirely and even greatly exceed the openings pierced underneath them in a manner such that they exhibit no free and movable end which would be capable of being soldered to a surface electrode of a first substrate which would be provided with an underlying hole such as that shown for instance in the document FR-A No. 2 439 438. Contrary to this and as will appear subsequently, the present invention proposes printed conductors which present extremities capable of being bent in a manner such that they may be introduced into holes giving access to the electrodes of the module, then soldered to these electrodes.
The purpose of the invention is to provide a satisfactory solution to the different problems which have been evoked hereinabove.